Speedometer.



Al SPEEDQMETER.

APPLlCATi0N FILED mac. 26. 1913.

Patented Sept. 3, 1918.

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ALEXANDER DEY, Oli EDINBURGH, SCOTLAND.

sPEEnoi/Ln'rna i Specification of Letters Patent. Patented Sept. 3,1918.

Application filed December 26, 1913. Serial No. 808,755

To all whom it may concern:

Be it known that I, ALEXANDER ,DEY, a subject of the King of GreatBritain, residing at Edinburgh, Scotland, have invented certain new anduseful Improvements in Speedometers, of which the following is aspecification.

This invention relates to instruments for measuring or indicatingspeedand. is adapted to indicate the rate of'rotation of a rotatable member,such as a machine element or vehicle wheel, it being particularly .de-

igned for indicating the speed of travel of a vehicle. p v

Ithas heretofore beenvproposedto utilize a column of liquid forcedupward by centrifugal force caused by the action of a fan or otherwise;to indicatethespeed of a rotatable member, but difficulty has beenexperienced for the reason that the rise of the column of liquid wassubstantially proportional to the square of the velocity of rotation andtherefore was excessive for high velocities. As a result anabnormallylong column of liquid was required and its rise was so rapld as to bebeyond control and incapable of accurate measurement.

Fig. a is a sectional view on line I V IV .of Fig.

'Beferring to the drawings in detail, the

numeral 1 designates a channel, preferably substantially vertical, inwhich the indicating fluid is caused to rise by any suitable means dependent'upon the velocity of rotaj t on of the part whose speed is to bemeas- 'ured. This channel may be of any suitable construction and themeans for causing the I rise of the column of fluid may be ofany,desired nature adapted to accomplish the intended purpose. As shown thelower end of the channel 1 is connected by'means of a duct 2 to achamber 3 in which isrotated a fan 4. The fan l comprises a pair ofblades secured to a sleeve 5, which is attached at its .upper end to ashaft 6. The shaft 6 is connected to be driven from the part whosespeedof rotation is to be measnred, any suitable means bemg provided forthis purpose, for example, a eXible torsion shaft 7'. A 'A reservoir fortheindicating fluid is preferably provided above the chamber 3, thisreservoir in the present instance comprising a conical chamber 8 whichis partly" separated from the chamber 3 by a partition 9. The fluidislperniitted to flow from the chamber 8 to the chamber, 3 throughthenarrowspace 10 around the sleeve 5.

lt is usually most convenient to have the shaft for imparting motion tothe fan enter the apparatus at the bottonrand in order gto p eyentleakage front the chamber I My present invention relates primarily tomeans for obviating this difficulty by providing for the control of therise of the liquid within the desired limits It is possible by myinvention to make the riseof t l u d: 9 1 11 1 dir tly. ror f t i so esflqc an esmaee i laay hu elea l rel .w u. t i 1 i lli ehiw ieseal'teaeftit ltl zfi li It f hirti th anemiaelsecem e ies-s ta, aaaiaaaa. 11Ii,aa ra remen samis. i e e?" wa /sati math re i ei A t b 1 hara'cterbvi tni iuietse ofkstuffili holis are eemekiditne baa-ac f at ,liaifiteri 1; mm: J 'i Mim' out? it 1 H twig-i1 tow ama *i'u Winne 0 Fianna 4 E"his: in ,rmea aa aere i rea i e-ta a We areieaedatas a Wise 1: .fl itrrevent nai rennet. l I t s e iie, lg so t i a r "th 2 t n e n u u' g uet; x 1' n fliiic we" amine channel and means for returning the overflowmay be of any suitable nature, but I prefer to construct this part ofthe apparatus as follows: 7

A tubular casing 12 is connected to the top of the reservoir 8 and hasformed in 'one side a substantially vertical depression lower end of thetubular casing 12, a washer or packing 16 of rubber or other suitablematerial being preferably interposed at this point in order to form atight joint. The glass tube is held in position by a cap 17 which alsocloses the upper end of the tubir lar chamber of the apparatus. The cap17 may be secured in place in any suitable manner, asby screwing it upona threaded extension 18 of the tubular casing 12, a washer or packing 19being interposed betweenthe cap and the end of the glass tube. Byscrewing down the cap, the glass tube is firmly held between the packingl6 and 19, and the channel and easing of the appara tus are thuseflectually sealed. The glass tube 1 1 preferably fits the tubularcasing snugly so as to prevent the escape of the liquid out of thechannel 1, but this fit need not be absolutely tight, as the glass tubeentirely surrounds the metal part 12 and therefore prevents evaporationeven if some leakage out of the channel is possible.

The device is normally filled with liquid up to the level of the top ofthe conical chamber 8 and the bottom of the glass tube.

Ilpon the rotation of the shaft 6, which revolves the sleeve 5 and fanblades 41, the fluid in the chamber 3 isthrown outwardly and theresulting pressure causes the fluid to rise in the column 1. Ordinarilythe pressure in the chamber 3 will increase proportionately to thesquare of velocity of rotation ofthe fan, which would tend to cause thefluid in the column to rise proportionately to the square of thevelocity. This has been found objectionable in previous speedometers ofthe fluid type for the reason that at the higher velocities the rise ofthe column is so rapid as to be beyond control and to renderthe deviceineffectual for the purpose for which it is intended. The length of thechannelrequired is excessive and has rendered such devices impractical.V

In accordance with the present invention, vmeans are provided forovercoming this defect and controlling the risev of the column so as tokeep the same within the desired limits. This result is accomplished vbefastened to any by providing one or more outlets at suitable points inthe channel, which permit the escape of some of the fluid therefrom andso reduce the rate of rise of the column. In the particular embodimentof my invention shown, I have provided a series of holes 20, 21 and 22through the wall of the groove or depression 13. These holes may be ofsuch suitable number, size and position as may be found necessary toeffect the desired operation. I have shown three holes arranged oneabove the other for this purpose, the upper hole 22 being somewhatsmaller than the other two, but I do not wish to limit myself to thisnumber of holes or to the relative proportion or spacing thereof. Theupperend of the channel is preferably open, as indlcated at 23, so thatat excessive speeds, the liquid driven up the channel may overflow intothe tubular chamber 12 and return through it to the reservoir 8. Theshaft 6, tube 11, and sleeve 5 preferably project up into this chamber12, as indicated, though it is not necessary for them to projectentirely up to the too of the chamber as shown The fluid escapingthrough the holes 20, 21 and 22 also falls back through the chamber12'into the reservoir 8. I have found that the fluid discharged throughthese holes 7 in falling back to the reservoir, sometimes entraps airbubbles which tend to find their way back to the fan chamber and areforced from the latter up into the fluid column.

The presence of the air bubbles in the fluid column interferes with theaccurate reading of the device and I preferably provide means forbreaking up and eliminating the same. For this purpose, it is simplynecessary to provide a screen or baflie plate in the lower a part of thechamber 12 or reservoir 8 which the returning fluid must pass. I haveillustrated suitable means for this purpose comprising an inverted cone2 1 secured to the wall of the chamber 8, throughout a part of itsperiphery as indicated at the points 25.

Narrow spaces are left at 26 between the periphery of the cone-shapedbalfle plate and the inner wall of the chamber 8 and a narrow space 27is left around the sleeve 5. The passage of the fluid through thesenarrow spaces breaks up and removes the air bubbles. This process isfurther effected by the passage of the fluid through the narrow space10, where the sleeve 5 passes through the partition 9.

In order that the position of the top of the fluid column may be readilyobserved, a

float 28 may be carried upon the same if desired. The deviceispreferably inclosed in.

a suitable case 29, which serves to'protect the apparatus and present anattractive appearance, and by which the apparatus may suitable support.The front of the case is provided with a slot30 through which the liquidcolumn may be ob- I vided to measure the rise of-the column.

For indicating the speed of revolution of a piece of machinery, thisscale-may be divided to show revolutions per minute, or other desiredunit, while for registering the speed of a vehicle, the scale ispreferably divided to indicate miles per'hour.

By properly p'roportioning the outlets in the channel, it is possible tosecure a substantially uniform rise of the fluid column for uniformincrements of speed and thus to use a scale divided equally throughoutor substantially throughout its height. This is of decided advantage asit facilitates the accurate reading ofthe instrument.

The operation of the apparatus will be apparent from the foregoingdescription. hen the fan is at restthe fluid level is at the bottom ofthejchannel "1 and indicates zero. Upon the rotation of thefan 4:, thefluid column is forced up the channel carrying the float 2'8 with it. Asthe speed in creases, the column rises uniformly, any ex: cessive risebeing prevented by the overflow of a part of the fluid through one ormore of the outlets in the channel. As the column rises, the outflowincreases and partly compensates for the increase of pressure due to thegreater velocity of the fan so that a uniform or any desired rate ofrise of the column may be secured.

The fluid system ofthe apparatus as a whole is hermetically sealed, sothat evaporation of the fluid is effectually preventedand a constantvolume of fluid maintained within the device, thus securing accurateindication at all times.

While I have illustrated in the drawing and described in detail onespecific embodiment of my invention, it is to be understood that I donot limit myself to the details thereof, but the principle of myinvention is capable of embodiment in other forms of apparatus, and I,therefore, intend to cover my invention in its various applicationsbroadly.

Having thus described my invention, I claim:

1. In a speedometer, the combination of a chamber, a rotatable fantherein, a liquid reservoir above said chamber, a channel above saidreservoir, a duct connecting the peripheral portion of said chamberto'the lower end of said channel, the wall of said channel having anoverflow outlet therein, means for returning the overflow from saidoutlet to said reservoir, and constantly operative means for removingair bubbles from the liquid flowing back to said reservoir.

2. In a speedometer, a channel for a fluid indicating column comprisinga perforated metal rear Wall and a glass front wall,

3. In a speedometer, the combination of a chamber, a liquid actuatingmember thereiii and a channel for a liquid indicating columncoiineetedat itslower end with said chamber, said chamber comprising a perforatedmetal rear wall and a glass front wall.

4. In a speedometer, the combination of.

a chamber, a fluid actuating member therein, a hollow metallic casingabove said chainber, a portion of the outer wall ofsaid casing form ngone wall of a channelforthe indicating fluid column, a transparentmember engaging SZLlLlCEL-SIHQ, forming the other wall of said channel.7

5. In a speedometer, the combination of a chamber, a rotatable fluidactuating member'therein, a tubular casing above saidv chamber, saidcasiiig having a substantially vertical depression or groove -'in oneside thereof, and a glass; tube inclosiiig said tubular 'casii g, thewall of said groove and a for the fluid column. 7

g 6, In a speedometer, the combination ,of a; chamber, a rotatablefluidactuating memportion of said glass tube forming a channel b'er therein,a tubular casing above said chamber, said casing having a substantially7 vertical depression or groove in one side thereof, and a glass tubeinclosing said tubular casing, the wall of said groove and a portion ofsaid glass tube forming a channel for the fluid column, the wall of saidgroove being perforated.

7. In a speedometer, the combination of a chamber, a rotatable fluidactuating member therein, a fluid reservoir above said chamber, atubular casing above said reservoir, said casing having a substantiallyvertical depression or groove in one side thereof, and a glass tubeinclosing said tubular casing, the wall of said groove and a portion ofsaid glass tube forming a channel for the fluid column, the wall of saidgroove being provided with a plurality of perforations spaced one abovethe other.

8. In a speedometer, the combination of a chamber, having an openinginthe bottom thereof, a tube secured to the bottom of said chamberaround said opening and projecting up throughthe chamber, a shaftprojecting up through said tube, a sleeve secured to the upper end ofsaid shaft, inclosing said tube and extending down into said chamber, afan mounted on said sleeve within thechamber, a liquid reservoir abovesaid chamber, a tubular casing connected with the upper end of saidreservoir, an annular seat around the lower end of said tubular casing,a glass tube surrounding said casing and resting on said seat, a capclosing the upper end of said tubular casing engaging the upper end ofsaid glass tube to clamp the same upon said seat, said tubular casinghaving a substantially vertical groove in one side thereof forming witha portion of the wall of said glass tube a sub- 7 necting the peripheralportion of said fan chamber with the lower end of said channel.

9. In a speedometer, the combination of a channel, a liquid indicatingcolumn therein the top of which constitutes a visible index, meansresponding to changes in speed for varying the height of the column, anda normally open overflow outlet in said channel above the lower endthereof permitting some of the liquid to flow out of said outletwhenever the top of the liquid column reaches or passes above the levelthereof.

10. In a speedometer or the like, a chamber containing a body of liquid,a channel connected therewith, means responding to variations of speedfor causing the liquid to rise in said channel, said channel having anormally open outlet therein permitting a part of the liquid as it risesin the channel to escape, means for returning the liquid which escapesto the chamber, and constantly operative means for removing air bubblesfrom the returning liquid.

11. In a speedometer or the like, a chamber containing a body of liquid,a channel .connected therewith, means responding to variations of speedfor causing the liquid to rise in said channel, said channel having anormally open outlet therein permitting a part of the liquid as it risesin the channel to escape, means for returning the liquid which escapesto the chamber, and means providing narrow passage ways through whichthe returning liquid must pass for removing air bubbles from saidliquid.

In witness whereof I have hereunto set my hand, in the presence of twosubscribing witnesses, this 6th day of December, 1913. ALEXANDER DEY.

Witnesses:

FREDERICK PIA'rT, Gnomes WHITELAW.

I Eopies of this patent may be obtained for five cents each, byaddressing the Commissioner of Patents,

Washington, D. 0.

